The Spacefaring Power of Pee

August 31, 2019

In the “The Martian,” astronaut Mark Watney
uses a slightly…smelly source of fertilizer to grow food on Mars, mixing Martian dirt
with feces to create soil for his potatoes. But the idea of using human by-products on
a deep-space exploration mission isn’t so far-fetched. In fact, it’s probably essential if we want
to make the months-long trip to the red planet for realsies. Human waste is inevitable, but rather than
thinking of our bathroom leavings as a dead end, space researchers see them as an appealing
resource. Astronauts on the International Space Station
already drink their own urine. Ever since 2009, filtration systems on the
station have been able to convert water from sweat, showers, and yes, pee into drinking
water. In a multi-step process, the water is carefully
filtered by vacuum distillation. Then it’s treated with iodine to kill any
bacteria and comes out squeaky clean. It does in the US-built part of the station,
anyway. The Russian-built water reclamation system
doesn’t use urine. Which means whenever the astronauts get a
chance, they haul bags of pee from the Russian side and feed it into the American reclamation
system. No point in letting that water go to waste. Water isn’t the only thing in urine. It’s packed with carbon and nitrogen, locked
up in a molecule called urea. It’s a good bet that if a molecule has carbon
and nitrogen in it, then there’s a microorganism that can eat it. Which is how researchers from Clemson University
plan to convert astronauts’ urine into plastics and nutrients using some mighty microbes. Specifically, yeast. Yeast are super great. They give us beer, bread, and in the future,
maybe brain food. This little superhero is called Yarrowia lipolytica. To grow it in space, astronauts would feed
it algae grown from the recycled carbon in their breath. But it would also need nitrogen. Fortunately, it thinks pee is delicious. With all that tasty good stuff from breath
and pee, this space yeast could become a living recycling plant. That’s because they are carbon master craftsmen. They’re great at making oils and fats, stringing
carbon together in long chains to produce a huge variety of energy-packed products. A little genetic tampering by humans can shape
what products they make, and how much of them. One thing the researchers want the yeast to
make is omega-3 fatty acids. You may have heard of these as the healthy
fats abundant in fish. They’re needed for proper brain function
and may improve heart health. Inconveniently, our bodies can’t make omega-3s. We have to get them in our diet. And as supplements, omega-3s have too short
of a shelf life to last through your joyride to Mars. So these yeast are being engineered to become
supplement powerhouses, producing omega-3s that astronauts can harvest from some of the
growing yeasties and eat. Which means the yeast will be making plenty
of brain food so our astronauts can continue scienceing. But that’s not all the researchers want
to harness this handy little yeast for. Future space missions will rely on 3D printers
to make tools and other things that astronauts will need on the fly. That 3D printer still needs plastic to make
things from, though. Enter our hero yeast once more. The fats and oils this yeast produces are
made mostly of carbon and hydrogen. But those same organic raw materials are also
what you need to make plastic. The yeast can actually be genetically engineered
to spit out PHAs, which are a kind of polyester — the same kind of plastic fiber that pops
up in your clothes. Which means this space-faring, pee-swilling
yeast could make not just nutritional supplements, but raw material for plastic tools that astronauts
can use. Just don’t think too hard about where that
wrench came from. The yeast makes plastic as a way of storing
food for itself to eat later. Yum, plastic. I love soda bottles, don’t you? That means it can be hard to get the PHAs
out of the yeast, which is holding on to its precious food supply. There could be a way to engineer the yeast
to feed right into the printer, but the researchers aren’t sure yet, and they might end up using
a more traditional extraction method. Basically, space researchers are thinking
hard about how to recycle everything astronauts touch–again and again and again–on an atomic
level. The yeast is just one way to tackle some of
these problems, and we’ll probably need lots of creative engineering to get astronauts
to Mars in one piece–and eventually, to bring Matt Damon home. Again. Seriously, why do we always have to keep saving
that dude!? Could you swallow supplements knowing they
were grown from last week’s pee? Let us know in the comments, and give the
thumbs up and subscribe buttons some love while you’re there. And hey, thanks for watching!